First- and second-order information in natural images: a filter-based approach to image statistics

Previous analyses of natural image statistics have dealt mainly with their Fourier power spectra. Here we explore image statistics by examining responses to biologically motivated filters that are spatially localized and respond to first-order (luminance-defined) and second-order (contrast- or texture-defined) characteristics. We compare the distribution of natural image responses across filter parameters for first- and second-order information. We find that second-order information in natural scenes shows the same self-similarity previously described for first-order information but has substantially less orientational anisotropy. The magnitudes of the two kinds of information, as well as their mutual unsigned correlation, are much stronger for particular combinations of filter parameters in natural images but not in unstructured fractal images having the same power spectra.     

Multiplexed toxin analysis using four colors of quantum dot fluororeagents

Quantum dots (QDs) have the potential to simplify the performance of multiplexed analysis. In this work, we prepared bioinorganic conjugates made with highly luminescent semiconductor nanocrystals (CdSe-ZnS core-shell QDs) and antibodies to perform multiplexed fluoroimmunoassays. Sandwich immunoassays for the detection of cholera toxin, ricin, shiga-like toxin 1, and staphylococcal enterotoxin B were performed simultaneously in single wells of a microtiter plate. Initially the assay performance for the detection of each toxin was examined. We then demonstrated the simultaneous detection of the four toxins from a single sample probed with a mixture of all four QD-antibody reagents. Using a simple linear equation-based algorithm, it was possible to deconvolute the signal from mixed toxin samples, which allowed quantitation of all four toxins simultaneously.     

Topographic profiling and refractive-index analysis by use of differential interference contrast with bright-field intensity and atomic force imaging

A methodology is described for phase restoration of an object function from differential interference contrast (DIC) images. The methodology involves collecting a set of DIC images in the same plane with different bias retardation between the two illuminating light components produced by a Wollaston prism. These images, together with one conventional bright-field image, allows for reduction of the phase deconvolution restoration problem from a highly complex nonlinear mathematical formulation to a set of linear equations that can be applied to resolve the phase for images with a relatively large number of pixels. Additionally, under certain conditions, an on-line atomic force imaging system that does not interfere with the standard DIC illumination modes resolves uncertainties in large topographical variations that generally lead to a basic problem in DIC imaging, i.e., phase unwrapping. Furthermore, the availability of confocal detection allows for a three-dimensional reconstruction with high accuracy of the refractive-index measurement of the object that is to be imaged. This has been applied to reconstruction of the refractive index of an arrayed waveguide in a region in which a defect in the sample is present. The results of this paper highlight the synergism of far-field microscopies integrated with scanned probe microscopies and restoration algorithms for phase reconstruction.     

Evaluation of two portable lead-monitoring methods at mining sites

Two methods for measuring airborne lead using field-portable instruments have been developed by the National Institute for Occupational Safety and Health (NIOSH): Method 7702 uses X-ray fluorescence (XRF), and Method 7701 employs ultrasonic extraction (UE) followed by anodic stripping voltammetry (ASV). The two portable methods were evaluated at mining sites. Area air samples were collected throughout two mills where ore from nearby mines was processed; the primary constituent of the ore was lead sulfide (galena). The air samples were collected on 37 mm mixed cellulose ester membrane filters housed within plastic filter cassettes. At the end of the work shift, the cassettes were collected and taken to a room off-site for analysis by the two portable methods. The filter samples were first analyzed by XRF and then by UE/ASV. Calibration was verified on both instruments according to standard procedures. The samples were then sent for confirmatory analysis via flame atomic absorption spectrometry (FAAS) according to NIOSH Method 7082. Pairwise comparisons between the methods using the paired t-test showed no statistically significant differences between ASV and FAAS (P>0.05); however, the comparison between XRF and FAAS was statistically significant (P<0.05). The elevated lead concentrations reported by XRF relative to FAAS were likely the result of the ability of XRF to report total lead, including lead silicates. This form of lead is not liberated in the digestion process prior to FAAS analysis, and is therefore not detected by this method. Despite this discrepancy, lead concentrations measured by both portable technologies were found to be highly correlated with the laboratory method (R2>0.96), suggesting that they are suitable as screening methods for airborne lead at mining sites.     

Biogeochemical processes and microbial characteristics across groundwater-surface water boundaries of the Hanford Reach of the Columbia River

Biogeochemical processes within riverbed hyporheic zones (HZ) can potentially impact the fate and transport of contaminants. We evaluated a modified freeze core technique for the collection of intact cobble-bed samples from the Columbia River HZ along a stretch of the Hanford Reach in Washington State and investigated microbiological and geochemical parameters of corresponding frozen and unfrozen samples. During three sampling periods (March, May, and November 2000), relatively high numbers of viable aerobic heterotrophic bacteria were recovered from both unfrozen (10(6)-10(7) cfu/g) and frozen samples (10(5)-10(6) cfu/g). Relatively large populations of sulfate-, nitrate-, and iron-reducing bacteria were present, and significant concentrations of acid-volatile sulfide were measured in some samples, indicating that anoxic regions exist within this zone. Cr(VI), a priority groundwater pollutant on adjacent U.S. Department of Energy lands, was probably removed from solution in HZ samples by a combination of microbial activity and chemical reduction, presumably via products of anaerobic microbial metabolism. These results suggest that biogeochemical processes in the Columbia River HZ may contribute to the natural attenuation of Cr(VI). Although freezing modestly diminished recovery of viable bacteria, freeze core techniques proved reliable for the collection of intact hyporheic sediments.     

Self-assembled nanoscale biosensors based on quantum dot FRET donors

The potential of luminescent semiconductor quantum dots (QDs) to enable development of hybrid inorganic-bioreceptor sensing materials has remained largely unrealized. We report the design, formation and testing of QD-protein assemblies that function as chemical sensors. In these assemblies, multiple copies of Escherichia coli maltose-binding protein (MBP) coordinate to each QD by a C-terminal oligohistidine segment and function as sugar receptors. Sensors are self-assembled in solution in a controllable manner. In one configuration, a beta-cyclodextrin-QSY9 dark quencher conjugate bound in the MBP saccharide binding site results in fluorescence resonance energy-transfer (FRET) quenching of QD photoluminescence. Added maltose displaces the beta-cyclodextrin-QSY9, and QD photoluminescence increases in a systematic manner. A second maltose sensor assembly consists of QDs coupled with Cy3-labelled MBP bound to beta-cyclodextrin-Cy3.5. In this case, the QD donor drives sensor function through a two-step FRET mechanism that overcomes inherent QD donor-acceptor distance limitations. Quantum dot-biomolecule assemblies constructed using these methods may facilitate development of new hybrid sensing materials.     

应用材料的光刻方案：图形vs．印制

虽然应用材料公司(Applied Materials)并不以光刻而闻名,但它还是想提醒大家:光刻不是只有印制(printing)。正如应用材料公司的薄膜事业群总经理Farhad Moghadam在SPIE的先进光刻会议的新闻发布午宴     

Words, music, and other measures: Predicting the repertoire popularity of 597 Schubert lieder.

To address the venerable aesthetic question of the relative importance of music and words, musical and textual characteristics were used to predict recording counts of 597 Franz Schubert lieder. Predictors included career variables (age and concurrent productivity), "whole song" variables (e.g., performance duration, structural complexity, major vs. minor key), thematic measures of the first six notes of the vocal incipit (e.g., melodic and rhythmic originality), poet variables (Goethe, Schiller, etc.), and text variables (computer content analysis measures of primordial and conceptual thought and positive and negative emotions). Many correlations between predictors were small but reliable; career variables accounted for most strong correlations. A 45-predictor regression model was highly significant (R2 = .63), with 13 reliable (p